In the conventional semiconductor devices, a semiconductor element (semiconductor chip) is mounted on a metal lead frame. In order to assure continuity with the outside, the aforementioned semiconductor element and the inner lead of the aforementioned lead frame are connected by bonding a metal wire. In addition, the aforementioned semiconductor element and lead frame are encapsulated with an epoxy resin composition.
With the recent advance in the high performance of electric products, mobile phones and the like, miniaturization, thinning and high performance are in demand for semiconductor devices as well. In order to realize this, semiconductor device forms such as TSOP (thin and small outline package), QFP (quad flat package) and the like have been developed. In addition, since the lead frame-type semiconductor devices have a limitation in terms of the number of external leads, development of BGA (ball grid array), LGA (land grid array) and the like which use balls and lands instead of leads for effecting continuity is also in progress.
Thus, with the advance of miniaturization and high performance gaining, pitch of metal wires inside the semiconductor device also became narrow, and some of the latest semiconductor devices have a metal wire pitch of less than 100 μm
On the other hand, the general production steps of the aforementioned epoxy resin composition for semiconductor encapsulation include the steps of mixing, melt kneading and pulverization, and friction and collision of the composing materials of the aforementioned epoxy resin composition for semiconductor encapsulation with the production device occur in each of these steps. Thus, the aforementioned epoxy resin composition for semiconductor encapsulation is contaminated with conductive foreign metallic particles derived from the aforementioned production device. Also, in addition to the aforementioned cause due to the production device, there is a case in which the aforementioned composing materials themselves are contaminated with conductive foreign metallic particles.
When the aforementioned semiconductor element is encapsulated with an epoxy resin composition for semiconductor encapsulation contaminated with such conductive foreign metallic particles, there is a possibility that the aforementioned foreign particles are caught between metal wires and the like and thereby cause a short-circuit, in the case of the aforementioned narrow pitch semiconductor device.
Accordingly, for the purpose of reducing contamination of the aforementioned conductive foreign metallic particles, a method for removing of the aforementioned conductive foreign metallic particles in the production process of the aforementioned epoxy resin composition for semiconductor encapsulation, for example, using a magnet, has been proposed (e.g., Patent Reference 1).
Patent Reference 1: JP-A-9-173890